Method of preparing creosoting compositions



Nov. 8, 1932.

S. P. MILLER METHOD OF PREPARING CREOSOTING COMPOSITIONS Filed De :.18.v 1928 Il l l Il :53' l: u Il lr :t 4/25 i: 1: l Il 'l |l INVENTOR NM 7mdk )und ATTORNEYS Patented Nov. 8, 1932 UNITEDl STATES PATENT OFFICE STUART PABHELEE MILLER, 0I' ENGLEWOOD, NEW JERSEY, ASSIGNOR TO THE BARRET COMPANY, OF NEW YORK, N. Y., A CORIOBATION 0F NEW JERSEY i HETH'OD 0F PREPARING CBEOSOTING OOMPOSITIONS Application illed December 18, 1928. Serial No. 326,773.

This invention relates to a new and improved method of preparing creosoting compositions. The new creosoting compositions are valuable substitutes for the ordinary coal tar solutions, so-called.

According to the present invention, hot

`-coke oven gases or gas retort gases carrying which tarry oil can be directly employed as a substitute for the ordinary creosoting compositions of the type known as coal tar solution. In specialcases it may be desirable to eliminate a part or all of the lighter oils from the tarry oils, or to add tar, or to add distillate oils to the tarry oils before use as creosoting compositions.

In making ordinary coal tar solutions, the greater part of the tar collected from the coke oven gases is distilled, and the distillate is blended with a relatively small proportion of undis'tilled tar, usually in the proportions of 80% of distillate to 20% of tar, to make the coal tar solutions of commerce. The distillation of this large amount of tar is expensive, and, when distilled by the usual methods, considerable decomposition of oil takes place during the distillation, with resulting loss of valuable oil, and corresponding increase in pitch production.

The proportlons 1n which coal tar is blended with coal tar distillates in makingy Vso-called free carbon. The specifications also usually limit the amount of low boiling distillate, for example, to not more than 5% distillate up to 210 C., and not over 25% up to 235 C., while limitations are also imposed' as to the character of the residue remaining after the distillation to a predetermined maximum temperature. According to the present invention, I subject the coke oven or gas retort ases tov a selective partial and incomplete c eaning to remove selectively therefrom a partfonly of the suspended heavy tar and pitch constituents, while leaving in the gases' a regulated portion of the suspended tarfand pitch constituents to be subsequently se arated from the gases byV further cooling.YA naddition, I carry out this regulated selective partial cleaning of the gases at a suiiciently high temperature to leave a large partof henormal oil content of the gases invaporform, so that, on subsequent cooling ofthe gasesthere is directly separated therefromatarry oil with a limited amount of heavyv tar constituents, the amount being such' that the oil as a whole, and the oil even after distillation to remove any excess of low-,boiling point constituents, will have a suiiiciently low content of so-called free carbon tol enable .it to be directly employed Without the addition of distillate oil for makingjcreosoting compositions. If the content of tarry matter as evidenced by the Vcontent of sofcalledl free carbon is not sufficient in the tarry oil recovered, additional tarcan be bl'endedrthere- With, but in any event the distillation of a large amount of tar to produce a large amount of distillate oils is made unnecessary.

The partial cleaning ofthe gases, yaccording to the present invention, isgcarried out in an electrical precipitator, but linstead of operating the precipitator in v the ordinary way to eifect substantially complete removal of suspended tar and pitch particles from the gases, I intentionally operate the recipitator so as to avoid such complete c eaning and to eect onlyA arselective partial and incomplete cleaningoffthe gases. This can be accomplished by usingin a recipitator having any particular size 'tu es, a regulated velocity at which cleaning is substantially complete so that the electrical precipitation 1s only a partial and incomplete cleaning of the cooling, give relatively clean oils substan\ tially free from heavy tar and pitch constituents. In the present process selected constituents of the gases are removed, instead of all suspended carbon and pitch constituents, and there is left in the gases the remaining suspended constituents which are not selectively removed by the partial and incomplete cleaning treatment.

In general, the electrical precipit-ator fon selectively and partially cleaning the gases is located between the collector main and the condensin system. It can be located immediately adJacent the collector main to receive the gases at the temperature at which they leave the collect-or main, and the gases leaving the preeipitator may then pass through the ordinary cross-over main tothe usual condensing system.

The temperature of the gases passing through the recipitator can be regulated by re ulating t ie cooling of the gases in the co lector main. Ordinarily, the gases in the collector main of a coke oven plant are cooled b the circulation of tar or ammonia liquor tlirough the main, or by spraying ammonia liquor into the gases passing through 'the main. Where such methods are employed, the cooling of the gases should be regulated so as to avoid cooling to too low a temperature since it is desirable that a considerable portion of the heavier oils remain in vapor form when the gases leave the collector main and pass through the electrical precipitator. The temperature of the gases can be increased by reducing the spraying of ammonia liquor into the collector main so that the gases can be passed through the electrical precipitator at a fairly high temperature, e'. g., at 200 C., or higher. The action of the precipitator is to separate out from the gases in a selective manner a part, but only a part, of the suspended heavy tar and pitch constituents carried in suspension therein,

. which constituents collect in the bottom of the main, the heavy tar or pitch from the precipitator, and the tarry oils -from the condensers. By maintaining the temperature of the gases sufficiently high, the oils condensed in the condensers will contain a large proportion of medium and heavy oils so that the tarry oils thus condensed can be directly employed in making creosoting compositions. In special cases it may be required to free it from lighter oils in order to meet particular specifications.

The temperature of the cleaning operation can be varied, the maximum temperature being that at which the precipitator can be operated without the deposit of constituents which do not readily flow therefrom. Temperatures which Will involve the separation of high melting point pitch in a non-liquid state, or carbonizing of pitch, should be avoided, but these temperatures will not ordinarily be met With in gases leaving the collector main of a by-product coke oven plant. The gases may be up to 250o or 300 C., or higher, or they may be at a lower temperature, around 200 or 150o C., or in some cases even lower.

The electrical precipitator employed may be of the usual design and operated with a. greatly increased gas velocity, as compared with gas velocities commonly employed; or the precipitator may be of shorter dimensions, that is, with shorter tubes, or With larger tubes, or it can be operated witha regulated potential lower than normal in order to eiect a partial but incomplete selective cleaning of the gases passing therethrough.

The invention will be further described in connection with the accompanying drawing Which shows in a more or less conventional and diagrammatic manner an arrangement v of apparatus suitable for carrying out the improved process at a coke oven plant.

In the accompanying drawing. the coke ovens are indicated conventionally at 5, each oven having an uptake pipe 6 leading to the collector main 7 Which may be cooled by the introduction of ammonia liquor by spray nozzles 8. The gases from the individual ovens pass through the individual uptake pipes into the common collector main.

From the collector main, the gases pass thru a suitable pipe connection to the electrical precipitator 9 which is arranged adjacent to the collector main so that the gases enter it at approximately the same temperature at which they leave the collector main. The precipitator and the connecting pipe may advantageously be insulated to avoid cooling of the gases passing therethrough,

and if desirable, the collector main may also be insulated.

The precipitator -may vary in form and construction. As shown it consists of a shell enclosing a number of tubes 10 supported in heads 11 andlQ within the shell. A gas inlet llo " ammonia, light oils, etc.

and distributing chamber at the bottom of the shell is shown with the baiiles 13. The precipit-ator has a plurality of electrodes 14 in the form of metal wires or rods weighted at 15 which extend through the tubes and are supported from the bus bar 16 located near the upper end of the tubes. The bus bar extends into chamber 17 and is supported upon insulators 18 and the bus bar is connected with a source of high tension current (not shown). The casing of the precipitator is grounded or otherwise connected to a source of current to complete thc circuit. The casing and tubes form the posit-ive electrode while the electrode connected to the bus bar is negative. The form and arran ement of the conductors in the circuit can e varied. High tension uni-directional current is supplied through the electrodes.

The precipitator has an outlet 19 for heavy tar or pitch separated from the gases, and an outlet 20 for the gases from which part of the suspended tar 'and pitch has been separated. The gases pass through the pi e 20 to the condensers 21 which may be o any suitable form and which is shown as an ordinary dlrect or Wet condenser 1n which the gases are cooled bythe direct introduction of Water or ammonia liquor into contact therewith so as to cool the gases rapidly and se arate the oils therefrom. The ases a ter leaving the condensers 21 pass t rough the line 22 to the usual apparatus for recovering A decanter 23 is arranged to collect the ammonia liquor and tarry oils condensed in t-he condensers. The water or ammonia liquor is drawn oii to the tank 24 and the tarry oils to the storage tank 25.

A by-pass 26 is provided for passing the gases around the precipitator when it may be necessary or desirable to disconnect the precipitator, and suitable valves are provided for directing the gases thru the precipitator or thru the by-pass.

In the operation 'of the apparatus and the carrying out of the process, the gasesare collected in the collector main in the ordinary way, or with limiting of the ammonia liquor sprays in the collector main so that the gases are at a somewhat higher temperature than is ordinarily maintained when they leave the collector main, .for example, the gases may be at a temperature around 150o C.. or 200 C.,

when they leave the. collector main, or they` resulted in the selective removal of only about of the suspended particles, leaving the remaining 30% in suspension to be subsequently separated in the condensers. In order to obtain the proper velocity, the number and aggregate cross-sectional area of the precipitator tubes can be regulated with reference tothe volume of gas passing through the collector main and cross-over main to the condensing system. If more convenient a voltage lower than required for complete cleaning can be employed, which is less eective in removing suspended. pitchV particles from the gases. In some cases it may be more convenient to employ precipitator tubes considerably shorter than used when complete clean'- ing is desired. In such a case the usual diameter of tubes and the usual voltage may be employed.Y Tubes two to four feet long may, for example, be substituted for the much longer tubes usually employed.

The extent to which the gases are selectively freed from entrained particles can be regulated with reference to the properties desired in the tarry oil recovered in the condensers. Where, for example, a tarry' oil is desired which requires less than 2% of socalled free carbon in it. this can be obtained by regulating the velocity of the gases thru the precipitator, or by regulating the voltage employed, to leave any desired proportion of the total heavy tar and pitch constituents in the gases. For example, in one case, a velocity of four feet per second resulted in substantially complete removal of the suspended particles and gave an oil in the condensers containing less than 0.1% of free carbon; while a velocity of about twenty-four feet per second in the same apparatus and with the same gas gave a tarry oil containing about 1.3% of free carbon. In any particular precipitator, if the velocity of the gases is fixed by the rate of production and the size of the precipitator, the regulation of the cleaning operation can be accomplished by the regulation of the potential or voltage. By regulation of the velocity of the gases, or the voltage, or other conditions, a tarry oil of any regulated content of tarrv or pitchy matter can be directly produced in the condensing'system.

The present process is thus one capable of regulation to produce tarry oils of regulated selective content of so-called free carbon, and otherwise of varying properties including the content of medium or high boiling point oils. This regulation is in part accomplished in the collector main by regulating the cooling of the gases and the temperature at which they pass to and thru the precipitator, by regulating the precipitating operation and the extent to which suspended heavytar and pitch constituents are selectively removed from the gases or left in suspension therein, and

regulating the subsequent cooling to separate tarry oil from the partially cleaned gases.

The tarry oils condensed in the condensers may be directly usable, without further treatment, for creosoting purposes, particularly where the gases are partially and selectively cleaned at a high temperature so that a large proportion of high boiling point oils are left in vapor form and subsequently condensed in the tarry oil in the condensers. By fractional condensation, any excess of low boiling point oils can be condensed separately in a later stage of the condensers, and kept separate. If the tarry oil contains too large a proportion of low boiling point constituents, it can be subjected to partial and limited distillation to remove such excess.

The tarry oils thus recovered do not ordinarily require the addition of coal tar distillate thereto to produce creosoting compositions therefrom. Their content ot so-call ed free carbon is sutiiciently low. However, if the content of free carbon is lower than that desired or permissible, addition of undistilled tar may be made to the tarry oils. Accordingly, all distillation of coal tar for the production of coal tar distillate is eliminated, and the creosoting compositions are directly pre ared at the by-product coke oven plant without-the need of distilling tar to produce coal tar distillate therefrom. The products of the operation are thus directly available as commercial products, particularly the pitch produced in the preciptator and the tarry oils produced in the condensers. The heavy tar separated in the collector main will require separate handling, although, if the collector main is operated at a high temperature, and with circulation of a large excess of hot tar or low melting point pitch in it, some distillation of the tar or pitch may take place to produce directly a mercha-ntable low melting point pitch as the product recovered in the collector main.

The present invention requires a minimum of change in the construction and operation of the ordinary by-product recovery system of a coke oven plant. It requires merely the interposition of an electrical precipitator in the cross-over main near the collector main, the provision of a receptacle for collecting the pitch from the precipitator, and the necessary electrical equipment to operate the precipftator in a selective manner, together with such regulation of the temperature in the collector main, with maintenance of higher gas temperatures in the collector main if necessary, to produce a heavier tarry oil in the condensing system.

The tarry oils produced according to the present invention, can be directly employed as creosoting compositions such as coal tar solution, thus eliminating the necessity of distilling tar for the production of the distillate oils commonly required for such coal tar solutions or improved creosoting compositions. They are distinguished by the absence of the carbon and pitch constituents which have been selectively removed by the selective partial cleaning treatment, and oo ntain the constituents which have not been so selectively removed.

I claim:

1. The improved method of producing tarry oils yielding not more than 5% distillate on distillation up to 210 C. in the by-product recovery system of coal distillation plants, which comprises cooling the coal distillation gases to a temperature not lower than 200 C., passing the gases at this temperature through an electrical precipitator, elfecting partial but incomplete separation of suspended constituents from such gases in the precipitator and subsequently cooling the gases to separate therefrom a tarry oil of low free carbon content and yielding on distillation-not more than 5% distillate upon distillation up to 210 C.

2. The improved method of producing tarry oils yielding not more than distillate on distillation up to 235 C. in the byproduct recovery system of coal distillation plants, which comprises cooling the coal distillation gases to a temperature not lower than 200 C., passing the gases at this temperature through an electrical precipitator, effecting partial but incomplete separation of suspended constituents from such gases in the precipitator and subsequently subjecting the partially cleaned gases to fractional cooling to separate therefrom a tarry oil of low free carbon content, yielding on distillation not more than 25% distillate on distillation to 235 C.

3. The improved method of producing tarry oils, yielding not more than 5% distillate on distillation up to 210 C. and containing not more than 2% of free carbon in the byproduct recovery system of coal distillation plants, which comprises collecting the gases rom the coal distilling units and passin these gases while at a temperature of 200 through an electrical precipitator, ell'ecting partial but incomplete separation of suspended constituents from such gases in the precipitator and subsequently cooling the gases to sepa-rate therefrom a tarry oil yielding not more than 5% distillate on distillation up to 210 C. and containing not more than 2% free carbon.

4. The improvement in the operation of the by-product recovery system of a coke oven battery whereby tarry oils yielding not more than 5% distillate on distillation up to 210 C. are produced, which comprises passing hot coke oven gases at a temperature of at least 150 C. through an electrical precipitator at such a velocity and subjecting them to such an electrical discharge therein that not more than of the suspended particles are precipitated from the gases and subsequently cooling the partially cleaned gases to separate therefrom a tarry oil of low free carbon content yielding not more than 5% distillate on distillation up to 210 C.

5. The improved method of producing creosoting compositions containing not more than 2% of free carbon and yielding not more than 5% distillate on distillation up to 210 C., which com rises collecting fresh hot coke oven gases rom a plurality of coke ovens in whichcoal is being` distilled and passing the gases while still at a temperature of at least 150 C., through an electrical precipitator, subjecting the gases in the precipitator to a partial but incomplete cleaning treatment so as toremove part of the particles suspended in the gases and leave part of the suspended particles in the gases and then subsequently cooling the partially cleaned gases to separate therefrom a tarry oil containing not more than 2% of free carbon and yielding not more than 5% distillate on distillation up to 210 C.

6. The improved method of producing v tarry oils yielding not more than 25% distillate on distillation up to 235 C. in

the by-product recovery system of coal distillation plants, which comprises cooling the" coal distillation gases to a temperature of from aboutl'O to about 300 C., subjecting the gases at this temperature to a pirtial but incomplete cleaning to remove only part of the suspended constituents from the gases, subjecting the partiallycleaned gases to fractional cooling to separate therefrom a tarry oil of low free carbon content yielding not more than 25% distillate on distillation to 235" C. i

7 The improved method of producing creo. soting compositions containing not more th an 2% of free carbon and yielding not more than 5% distillate on distillation up to 210 C., which comprises collecting fresh hot coal distillation gases from a plurality of coke ovens in which coal is being distilled `and subjecting the gases While still at a temrature of at least 150 C. to a partial but incomplete cleaning so as to remove therefrom a part only of the particles suspended in the gases and subsequently cooling the partially cleaned gases to separate therefrom a tarryy oil containing not more than 2% of .free carbon and yielding not more than 5% distillate on distillation up to 210 C.

In testimony whereof I alix my signature.

STUART PARMELEE MILLER. 

